Synesthesia

1. Synesthesia

Synesthesia is when the idea of a sense impression occurs as a reaction to another sense. For example, when one can taste something you feel (Apple Dictionary).

2. grapheme-color synesthesia

This is when letters and numbers are perceived as colors. This is the most usual case of synesthesia, and the most studied (Wikipedia.org).

3. ordinal-linguistic personification   

This is when animate-qualities or personalities are given to units such as letters, numbers, days and months (http://www.ncbi.nlm.nih.gov/pubmed/17381259).

4. number-form synesthesia

This type of synesthesia is a combination of number maps that involuntarily appears when an individual with this condition thinks of a number (Wikipedia.org).

5. sound-color synesthesia

Sound color synesthesia is when after a certain sound has the appearance of a distinct color. Quite a number of musicians experience this (http://articles.cnn.com/2009-02-09/health/synesthesia.genes_1_synesthesia-brain-regions-visual-areas?_s=PM:HEALTH).

6. lexical-gustatory synesthesia

One of the rarest forms of synesthesia, lexical-gustatory synesthesia is when taste sensations arise because of written or spoken words (Wikipedia.org).